[6] ARTIFICIAL PROPAGATION OF OYSTERS. 745 



the large number of eggs which never advanced in development was 

 constantly noticeable. Many had apparently escaped the attack of 

 spermatozoa, and many more only advanced through the very earliest 

 stages of segmentation. This was the case very frequently with the 

 eggs taken from oysters that were, so far as could be judged, perfectly 

 ripe, the eggs under the microscope appearing free from granular mat- 

 ter, well defined and of clean outline, well-shaped, and germinative 

 vesicle obvious. The frequent recurrence of this circumstance leads me 

 to believe that the eggs of even one oyster are not all ripe at the same 

 time, though they may approximate to it.' It seems very desirable that, 

 as recommended by Mr. Ryder, the histology of the ovaries should be 

 exhaustively studied, that the matter may be settled; its importance 

 to future experiments and to practical work is too obvious to need com- 

 ment. One other point may be mentioned in this connection. I found 

 one female oyster at Beaufort and one at Fair Haven with the visceral 

 mass, including the ovaries, filled with Bucephalus cuculns. 1 have not 

 met with any similar case, and consequently, the evil must be excep- 

 tional; but that it is possible is certain, and that possibility is an addi- 

 tional reason for using care in selecting the ova for artificial impregna- 

 tion, as the presence of bucephalus as well as infusoria in large numbers 

 in the water of the aquaria will conduce to failure. Dr. Brooks, in his 

 account of the initial experiment, has described the appearance of the 

 generative fluids when in proper condition, and I need not duplicate 

 his work. I only desire to impress my conviction that success or fail- 

 ure of experiments in this field is due, to considerable extent, to the 

 care, or want of it, in selecting the oysters from which are taken the 

 products of generation. 



2. Impregnation of the egg. — The methods followed and advised by 

 Brooks should be strictly adhered to. The males should be first treated, 

 and care should be taken that not more spermatozoa is used than is 

 necessary. One male will supply sufficient for half a dozen females, 

 but it is better to use a larger number and only partially wash out the 

 spermaries. In both sexes the ripe fluid is most easily removed, and 

 though after the first washing there appears in the crystal or saucer a 

 large amount of generative matter, yet most of it is probably unripe 

 and had better be thrown away. A perusal of Brooks' notes on the 

 structure of the generative organs will be sufiicient to convince any one 

 that the course I recommend will have its influence in preventing- un- 

 ripe ova or spermatozoa from getting into the aquarium jars; and, as 

 I have stated, the insurance of this point is a matter of importance. 

 The impression derived from Dr. Brooks' paper has been strengthened 

 by the experience of the past season, and I am of the opinion that in 

 several of the experiments I would have had more swimming embryos 

 had I not had so many eggs; many never developing and only polluting 

 the water. 



In removing the generative organs, the time and labor expended iii 



